Friction stir welding (FSW) is known as a method of joining metal members together. The friction stir welding is a technique of rotating and moving a rotary tool along a butted portion of metal members, allowing the metal at the butted portion to be plasticized and fluidized with heat generated by friction between the rotary tool and the metal members, and joining the metal members together in solid phase.
In recent years, as an electronic device as typified by a personal computer has been improved in performance, a calorific value of a CPU (heat generating body) installed therein has been increasing in amount and thus it has become important to cool the CPU. In conventional art, a heat sink of an air cooling fan system has been used to cool the CPU, but problems such as noises caused by the fan and cooling limits by the air cooling system have gain prominent attention. Thus, a liquid-cooled jacket has gathered attention as a next-generation cooling system.
As a method of manufacturing a liquid-cooled jacket, Patent Literature 1 discloses a technique of joining metallic components together by means of friction stir welding. FIGS. 29A and 29B are views showing a manufacturing method for a first conventional liquid-cooled jacket, in which FIG. 29A is an exploded perspective view, and FIG. 29B is a cross-sectional view of main parts showing a joining state. As shown in FIG. 29A, the first conventional liquid-cooled jacket is composed of a box-shaped jacket body 100 which opens upward, and a plate-shaped sealing body 110 which seals an opening of the jacket body 100.
The jacket body 100 is composed of a bottom portion 101 and a side wall portion 102 provided to stand on the bottom portion 101 and having the form of a rectangular frame in planar view. The jacket body 100 includes a recess 103 formed therein. Moreover, a stepped portion 104 is formed along a circumferential edge of the opening on an end surface of the side wall portion 102. As shown in FIGS. 29A and 29B, the manufacturing method for the first liquid-cooled jacket includes placing the sealing body 110 on the stepped portion 104 and then moving a rotary tool 120 being rotated along a butted portion of the jacket body 100 and the sealing body 110 to carry out friction stir welding.
The rotary tool 120 is composed of a cylindrical shoulder portion 121 and a stirring pin 122 projecting from a lower end surface of the shoulder portion 121. The rotary tool 120 is allowed to move once around the sealing body 110 along the butted portion while pressing the lower end surface of the shoulder portion 121 by about several millimeters into the jacket body 100 and the sealing body 110, thereby allowing the liquid-cooled jacket having a hollow portion internally to be formed. In this process, a plasticized region W is formed on a movement locus of the rotary tool 120.
On the other hand, FIGS. 30A and 30B are views showing a manufacturing method for a second conventional liquid-cooled jacket, in which FIG. 30A is an exploded perspective view, and FIG. 30B is a cross-sectional view of main parts showing a joining state. As shown in FIG. 30A, the second conventional liquid-cooled jacket is composed of a box-shaped jacket body 100 which opens upward, and a plate-shaped sealing body 110 which seals an opening of the jacket body 100.
The jacket body 100 is composed of a bottom portion 101 and a side wall portion 102 provided to stand on the bottom portion 101 and having the form of a rectangular frame in planar view. The jacket body 100 includes a recess 103 formed therein. As shown in FIGS. 30A and 30B, the manufacturing method for the second liquid-cooled jacket includes placing a back surface 110b of the sealing body 110 on an end surface 102a of the jacket body 100 and then moving a rotary tool 120 being rotated along an overlapped portion H formed by overlapping back surface 110b with the end surface 102a, to carry out friction stir welding.
The rotary tool 120 is allowed to move once around the recess 103 along the overlapped portion H while pressing the lower end surface of the shoulder portion 121 by about several millimeters into the sealing body 110, thereby allowing the liquid-cooled jacket having a hollow portion internally to be formed. In this process, a plasticized region W is formed on a movement locus of the rotary tool 120.